Public CA for secure clusters

General
#1

This link https://www.cockroachlabs.com/docs/stable/create-security-certificates-custom-ca.html mentions using an “external public CA”.

However my understanding is that the authentication mechanism is somewhat limited, in that it trusts any incoming connection if the CN=node and is signed by the same CA, and the IP address is listed in the server node’s Subject Alternative Name fields.

ie: if we had a multi-cloud deployment with a public proxy to proxy replica connections and placed that IP in the Subject Alternative Name fields, and we used a public CA (ie: Let’s Encrypt), then anybody could join our cluster.

If this is correct there should be a large warning, or better wording to recommend against using public CA’s.

#2

In theory you’re right, but in practice no public CA will give you a cert with CN=node. It’s only really possible to use public CAs for the UI certificate at this point. The docs could certainly be more clear about this; I’ve filed ana issue for this.

We’re also working on some improvements that would make it possible and safe to use other CAs including public ones.

#3

Also, Letsencrypt (mentioned explicitly on that page) don’t issue certificates with IP address in the subjectAlternateName - although it’s possible they might in future.

More context linked from here.